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                [Usaco2012 Feb]Symmetry                </h1>
                <p>时间限制：5s&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;  空间限制：128MB</p>			</div>
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                                <h3>题目描述</h3><p><p><span style="font-size: larger"><span class="Apple-style-span" style="word-spacing: 0px; font: medium Arial,Microsoft Yahei,Simsun,sans-serif; text-transform: none; color: rgb(0,0,0); text-indent: 0px; white-space: normal; letter-spacing: normal; border-collapse: separate; orphans: 2; widows: 2; webkit-border-horizontal-spacing: 0px; webkit-border-vertical-spacing: 0px; webkit-text-decorations-in-effect: none; webkit-text-size-adjust: auto; webkit-text-stroke-width: 0px"><span class="Apple-style-span" style="font-family: monospace">After taking a modern art class, Farmer John has become interested in finding geometric patterns in everything around his farm. He carefully plots the locations of his N cows (2 &lt;= N &lt;= 1000), each one occupying a distinct point in the 2D plane, and he wonders how many different lines of symmetry exist for this set of points. A line of symmetry, of course, is a line across which the points on both sides are mirror images of each-other. Please help FJ answer this most pressing geometric question. </span></span></span></p>
<p><span style="font-size: larger">上过现代艺术课后，FJ开始感兴趣于在他农场中的几何图样。他计划将奶牛放置在二维平面上的N个互不相同的点(1&lt;=N&lt;=1000),他希望找出这个点集有多少条对称轴。他急切地需要你帮忙解决这个几何问题。<br />
</span></p></p><hr/><h3>输入格式</h3><p><p><span style="font-size: medium"><span class="Apple-style-span" style="word-spacing: 0px; font: medium Arial,Microsoft Yahei,Simsun,sans-serif; text-transform: none; color: rgb(0,0,0); text-indent: 0px; white-space: normal; letter-spacing: normal; border-collapse: separate; orphans: 2; widows: 2; webkit-border-horizontal-spacing: 0px; webkit-border-vertical-spacing: 0px; webkit-text-decorations-in-effect: none; webkit-text-size-adjust: auto; webkit-text-stroke-width: 0px"><span class="Apple-style-span" style="font-family: monospace">* Line 1: The single integer N. </span></span></span></p>
<p><span style="font-size: medium"><span class="Apple-style-span" style="word-spacing: 0px; font: medium Arial,Microsoft Yahei,Simsun,sans-serif; text-transform: none; color: rgb(0,0,0); text-indent: 0px; white-space: normal; letter-spacing: normal; border-collapse: separate; orphans: 2; widows: 2; webkit-border-horizontal-spacing: 0px; webkit-border-vertical-spacing: 0px; webkit-text-decorations-in-effect: none; webkit-text-size-adjust: auto; webkit-text-stroke-width: 0px"><span class="Apple-style-span" style="font-family: monospace">* Lines 2..1+N: Line i+1 contains two space-separated integers representing the x and y coordinates of the ith cow (-10,000 &lt;= x,y &lt;= 10,000). </span></span></span></p>
<p></p></p><hr/><h3>输出格式</h3><p><p><span style="font-size: medium"><span class="Apple-style-span" style="word-spacing: 0px; font: medium Arial,Microsoft Yahei,Simsun,sans-serif; text-transform: none; color: rgb(0,0,0); text-indent: 0px; white-space: normal; letter-spacing: normal; border-collapse: separate; orphans: 2; widows: 2; webkit-border-horizontal-spacing: 0px; webkit-border-vertical-spacing: 0px; webkit-text-decorations-in-effect: none; webkit-text-size-adjust: auto; webkit-text-stroke-width: 0px"><span class="Apple-style-span" style="font-family: monospace">* Line 1: The number of different lines of symmetry of the point set. </span></span></span></p></p><hr/><h3>样例输入</h3><pre>4
0 0
0 1
1 0
1 1
</pre><hr/><h3>样例输出</h3><pre>4</pre><hr/><h3>提示</h3><p>没有写明提示</p><hr/><h3>题目来源</h3><p>Gold</p>
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